// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2015 Olga Diamanti <olga.diam@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.

#ifndef IGL_PARALLEL_TRANSPORT_ANGLE
#define IGL_PARALLEL_TRANSPORT_ANGLE
#include "igl_inline.h"

#include <Eigen/Core>
#include <vector>

namespace igl {
  // Given the per-face local bases computed via igl::local_basis, this function
  // computes the angle between the two reference frames across each edge.
  // Any two vectors across the edge whose 2D representation only differs by
  // this angle are considered to be parallel.

  // Inputs:
  //   V               #V by 3 list of mesh vertex coordinates
  //   F               #F by 3 list of mesh faces (must be triangles)
  //   FN              #F by 3 list of face normals
  //   E2F             #E by 2 list of the edge-to-face relation (e.g. computed
  //                   via igl::edge_topology)
  //   F2E             #F by 3 list of the face-to-edge relation (e.g. computed
  //                   via igl::edge_topology)
  // Output:
  //   K               #E by 1 list of the parallel transport angles (zero
  //                   for all boundary edges)
  //
template <typename DerivedV, typename DerivedF, typename DerivedK>
IGL_INLINE void parallel_transport_angles(
const Eigen::PlainObjectBase<DerivedV>&V,
const Eigen::PlainObjectBase<DerivedF>&F,
const Eigen::PlainObjectBase<DerivedV>&FN,
const Eigen::MatrixXi &E2F,
const Eigen::MatrixXi &F2E,
Eigen::PlainObjectBase<DerivedK>&K);

};


#ifndef IGL_STATIC_LIBRARY
#include "parallel_transport_angles.cpp"
#endif


#endif /* defined(IGL_PARALLEL_TRANSPORT_ANGLE) */